Study On The Antifouling Performance Of PSF Ultrafiltration By Surface Modification

The polysulfone membrane(PSF)had wide application prospect in the ultrafiltration process,because of its chemical stability was good,have a wide range of p H tolerance,and cheap,large temperature operation.But PSF had the low surface energy,strong hydrophobicity,it was easy to adsorb in the membrane surface and pore that separation,purification and concentration of the colloid proteins,organic and biological solution,caused membranep ermeation flux decreases and fouling problems.Therefore,in order to reduce the pollution of PSF that improved the efficiency of separation,membrane flux,and prolong its service life,hydrophilization modified of PSF has becomed one of the main content of membrane science.This paper studied the low-temperature nitrogen plasma modified polysulfone(PSF)ultrafiltration membrane fouling properties.By changing the pressure,power and time three variables of PSF membrane surface to obtain contact angle,obtain low-temperature nitrogen plasma modified PSF in the best condition;By synchronizing method,two-step grafting polymerization of acrylic acid(AA);the wettability and anti-fouling of membrane were studied by measured the contact angle,water flux,BSA flux of the modified membrane and before.;The wettability of membrane were studied by measured the flux of water,soy protein and after water washing and Na OH solution washing of modified membrane and before.;The anti-fouling of membrane were studied by Calculation pollution rate,attenuation,alkaline wash water recovery rate and washing recovery rateof the modified membrane and before.The studies showed that:(1)The low temperature nitrogen plasma treatment polysulfone membrane,contact angle reduced from the original 69° to 18.2° by being treated for pressure 5 Pa,power of30 W and process time of 90 s and 20 cm distance from discharge,hydrophilic can best.Through XPS element energy spectrum diagram analysis of membrane surface hydrophilicradical is introduced;Through SEM understand the polysulfone membrane modified membrane before and after the change of surface structure.(2)The optimal conditions of grafting acrylic acid was the optimal conditions for nitrogen plasma modification,grafting time in 2 hours,temperature of 50 ℃,the effect was better.Synchronization method,two-step grafting acrylic acid,and the comparative analysis and nitrogen plasma modified,it was concluded that the modification effect of grafting synchronization method was best,the deposition of acrylic acid and nitrogen plasma modified polysulfone membrane.(3)Modification of polysulfone membrane had well permeability,the pure water flux of membrane before and after modification from 21.5 L/h.(m2)increased to 36.0 L/h.(m2).Before and after the modification of membrane flux of soybean protein from 1.5 L/(m2·h)to 2.5 L/h.(m2).And polysulfone membrane modification can improve its pollution resistance,membrane before and after the modification of the attenuation rate fell from91.5% to 82.4%,the pollution rate fell 71.3% to 40.1%,water recovery rate from 51.5% to88.2%,alkaline recovery rate from 68.9% to 98.4%.(4)Soy protein flux were different in different p H conditions.The solubility was lower when p H equaled to or lessed than the isoelectric point,the highest amount of protein adsorption on the surface membrane,membrane flux decreases and vulnerabled to contamination of protein;When deviated from its isoelectric point,solution with charge that the solubility increase and reduced membrane pollution,so we should choose the suitable pH value.